The present invention relates to a method for adjusting an adaptive characteristics map of an adaptive engine-knock control system and a method for adaptively controlling the knock of an internal combustion engine.
A method for adjusting an adaptive characteristics map of an adaptive engine-knock control system is already known, where, in each case, current ignition-retard values are written to an adaptive characteristics map continuously, or in specific time intervals. In the event of a sharp change in the ambient conditions, for example when using a fuel that is less knock-resistant, the adaptive characteristics-map value is slowly adjusted as a function of the occurring knock signals, and each characteristics-map range must be entered at least once, in order to adjust the entire adaptive characteristics map.
A method for adaptively controlling the knock of an internal combustion engine is known from German Published Patent Application No. 40 08 170, where the current ignition-retard values are stored in an adaptive characteristics map. The adaptive characteristics map has subdivided ranges dependent on at least one operating parameter of the internal combustion engine, one value of ignition retard always being stored in the appropriate range, during operation. Upon shifting to another operating-parameter range, the ignition-retard value stored for this operating-parameter range forms the new ignition-retard value, which is the starting point for the engine-knock control. The characteristics-map value is adapted in the specific operating-parameter range in accordance with the signal of the engine-knock control system, the ignition being retarded in response to engine knock. If no engine knock occurs over a certain period of time, the ignition timing is advanced again.
In comparison with the known methods, the method of the present invention for adjusting an adaptive characteristics map of an adaptive engine-knock control system has the advantage that, in response to a sharp change in the ambient conditions, the ignition-retard value is immediately adapted without unnecessary engine knock occurring. It should be regarded as a further advantage, that the entire adaptive characteristics map is adjusted to the modified ambient conditions, which likewise results in prevention of unnecessary engine knock, and the new ambient conditions are already taken into consideration in response to changing to a new operating-parameter range. It is particularly advantageous that a change in the ambient conditions is detected, when the currently required ignition-retard value markedly differs from a reference angle corresponding to the specific operating-parameter range. Therefore, such a change in the ambient conditions may be detected easily and quickly. In this context, it is advantageous to generate a reference value from the current adaptive characteristics-map values. Upon detecting a change in the ambient conditions, it is also advantageous to calculate a factor, which describes which range between the worst possible adaptive characteristics-map value and the best possible adaptive characteristics-map value contains the current ignition-retard value, so that adaptive characteristics-map values may then be adjusted for each operating-parameter range in accordance with the factor. Thus, it is possible to adjust the entire adaptive characteristics map in a simple and quick manner. It is particularly simple to calculate the factor, when a straight line is interpolated between the best possible characteristics-map value and the worst possible characteristics-map value. It is likewise advantageous to establish the change in ambient conditions, using sensor values, since this allows the ambient conditions to be assessed in a more objective manner. The ambient temperature or the fuel quality especially influence the knock frequency. Therefore, is advantageous to monitor these conditions, using sensors. In the case of monitoring the ambient conditions, using sensors, it is also advantageous to characterize the new ambient conditions with respect to the best possible and worse possible ambient conditions, using a factor, as well as to ascertain the adaptive characteristics map adjusted to the new ambient conditions, using the factor. Consequently, it is once again possible to adjust the entire adaptive characteristics map in a simple manner. Furthermore, it is advantageous to design the adaptive characteristics map in a cylinder-selective manner and therefore adjust the adaptive characteristics map in a cylinder-selective manner, as well.
In comparison with the known method, the method of the present invention for adaptively controlling the knock of an internal combustion engine has the advantage that the ambient conditions are taken into consideration, it being possible to react very quickly to changed ambient conditions. In addition, it is advantageous that operating-state changes characterized by the occurrence of engine knock may be detected very quickly, it Since each cylinder or each cylinder group has its own combustion characteristics, it is, in this case, advantageous to implement the adaptive engine-knock control in a cylinder-selective or cylinder-group-selective manner.